x86: identify_cpu_without_cpuid v2

Krzysztof found some old cyrix cpu where an mtrr-alike cpu feature was
not detected properly.

this one is based on Krzysztof' patch, and we call ->c_identify() in
early_identify_cpu.

need to call c_identify() for cpus without cpuid even earlier ...

v2: Krzysztof point out need to give cyrix another chance about cpuid
    checking again, after ->c_identify() enables cpuid for it
Signed-off-by: NYinghai Lu <yhlu.kernel@gmail.com>
Cc: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/kernel/cpu/common.c

@@ -485,6 +485,33 @@ static void __cpuinit get_cpu_cap(struct cpuinfo_x86 *c)
 		c->x86_power = cpuid_edx(0x80000007);
 
 }
+
+static void __cpuinit identify_cpu_without_cpuid(struct cpuinfo_x86 *c)
+{
+#ifdef CONFIG_X86_32
+	int i;
+
+	/*
+	 * First of all, decide if this is a 486 or higher
+	 * It's a 486 if we can modify the AC flag
+	 */
+	if (flag_is_changeable_p(X86_EFLAGS_AC))
+		c->x86 = 4;
+	else
+		c->x86 = 3;
+
+	for (i = 0; i < X86_VENDOR_NUM; i++)
+		if (cpu_devs[i] && cpu_devs[i]->c_identify) {
+			c->x86_vendor_id[0] = 0;
+			cpu_devs[i]->c_identify(c);
+			if (c->x86_vendor_id[0]) {
+				get_cpu_vendor(c);
+				break;
+			}
+		}
+#endif
+}
+
 /*
  * Do minimum CPU detection early.
  * Fields really needed: vendor, cpuid_level, family, model, mask,
@@ -503,13 +530,16 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 #endif
 	c->x86_cache_alignment = c->x86_clflush_size;
 
-	if (!have_cpuid_p())
-		return;
-
 	memset(&c->x86_capability, 0, sizeof c->x86_capability);
-
 	c->extended_cpuid_level = 0;
 
+	if (!have_cpuid_p())
+		identify_cpu_without_cpuid(c);
+
+	/* cyrix could have cpuid enabled via c_identify()*/
+	if (!have_cpuid())
+		return;
+
 	cpu_detect(c);
 
 	get_cpu_vendor(c);
@@ -583,10 +613,14 @@ static void __cpuinit detect_nopl(struct cpuinfo_x86 *c)
 
 static void __cpuinit generic_identify(struct cpuinfo_x86 *c)
 {
+	c->extended_cpuid_level = 0;
+
 	if (!have_cpuid_p())
-		return;
+		identify_cpu_without_cpuid(c);
 
-	c->extended_cpuid_level = 0;
+	/* cyrix could have cpuid enabled via c_identify()*/
+	if (!have_cpuid())
+		return;
 
 	cpu_detect(c);
 
@@ -639,17 +673,6 @@ static void __cpuinit identify_cpu(struct cpuinfo_x86 *c)
 	c->x86_cache_alignment = c->x86_clflush_size;
 	memset(&c->x86_capability, 0, sizeof c->x86_capability);
 
-	if (!have_cpuid_p()) {
-		/*
-		 * First of all, decide if this is a 486 or higher
-		 * It's a 486 if we can modify the AC flag
-		 */
-		if (flag_is_changeable_p(X86_EFLAGS_AC))
-			c->x86 = 4;
-		else
-			c->x86 = 3;
-	}
-
 	generic_identify(c);
 
 	if (this_cpu->c_identify)